On Tue, Dec 06, 2016 at 11:56:56AM -0600, Jeremy Linton wrote: > Hi, > > On 12/06/2016 09:21 AM, Will Deacon wrote: > >On Fri, Dec 02, 2016 at 12:56:01PM -0600, Jeremy Linton wrote: > >>ACPI CPUs aren't associated with a PMU until they have been put > >>online. This means that we potentially have to update a PMU > >>definition the first time a CPU is hot added to the machine. > >> > >>Signed-off-by: Jeremy Linton <jeremy.linton@xxxxxxx> > >>--- > >> drivers/perf/arm_pmu.c | 38 ++++++++++++++++++++++++++++++++++++-- > >> include/linux/perf/arm_pmu.h | 4 ++++ > >> 2 files changed, 40 insertions(+), 2 deletions(-) > >> > >>diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c > >>index fa40294..4abb2fe 100644 > >>--- a/drivers/perf/arm_pmu.c > >>+++ b/drivers/perf/arm_pmu.c > >>@@ -711,6 +711,30 @@ static int cpu_pmu_request_irq(struct arm_pmu *cpu_pmu, irq_handler_t handler) > >> return 0; > >> } > >> > >>+static DEFINE_SPINLOCK(arm_pmu_resource_lock); > > > >Why do you need this spinlock? The hotplug notifiers are serialised afaik, > >and you don't take it anywhere else. > > Well, I assumed they were serialized, but then I went looking for a > guarantee and couldn't find one specific to the notifiers, even though the > previous lock was removed. They should be serialised either by virtue of them all running off the back of a single CPU (because the hotplug thread hasn't yet been created), or by the st->done completion for the hotplug work threads. Will -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
